Process for the manufacture of tetraethyl pyrophosphate



Unite States Patent 'fitice Patented Dec. 23, 1958 1 2 a vent andreaction medium, as for example, such .as .an i 9 aliphatic ketone,aliphatic ester, and the like Typical 4 1 examples of aliphatic ketonessuitable for use as solvents ePRQCESS THE 01; and reaction media areacetone, methyl ethyl ketone, TEI RAEI HYLPYRU HOSPHATE 5 diethylketone, methyl n-propyl ketone, methyl isobutyl 1,, ketone, methyl'amy'l ketone, diacetone alcohol, mesityl g i figg gt ggg gg g 52k 55 353; g j ig oxide, and the like. Typical examples of aliphatic esters a a.cbrporah-(mnf Virginia suitable for use as solvents and reaction mediaare methyl e acetate, ethyl acetate, ethyl formate, methyl formate, NorW ng- ,pp i a i n J n 21, 1956 10 et- 34 propi'onate, n-butyl acetate,isopropyl acetate, 2- 591131 ,728 ethylhexyl acetate, ethylene glycoldiacetate, etc It is 11 fi (CL believed that these ketones and estershave a moderate solvating action on the tetra-alkali metalpyrophosphates and thus inciease the reactivity between the mutuallyThis inv ntio'n'relates to a novel process for the-manu- 15 immiscibleor insoluble reagents, i. e. the ethyl chloride facture of tetraethylpyrophosphate and, more particuand thetetra-alkali metal pyrophosphates.In addition larly, to an improved process for the manufacture of theseketones and esters are otherwise unreactive to the tetraethylpyrophosphate from cheap and readily Iavailreagents employed in this:process. able industrial raw materials viz ethyl chloride and tetra-The catalyst for this process is, as aforesaid, an 'i'o'dide alkalimetal pyrophosphates. and, for purposes of this invention, includesiodine, hy- Tetraethyl pyrophosphate is a valuable organicinsecdro'iodic acid, ammonium iodide, the alkali metal iodides 'ticide,elfective in the control :of mites, aphids, thrips, and and thealkali-earth metal iodides. Such catalysts may a variety of otherinsects. It is usually pre ared in 'adb used in ant o ni n m n n y themore mixture with other isomeric, homologous and related of the catalystemployed the more rapid is the .rate of organophosphorus esters (such ashexaethyl tetraphosthe reaction, and satisfactory reaction rates andgood pha'te). When obtained in a pure state, it is a mobile, yields aregenerally obtained'by use of from 0:01 to 0 l0 amber-colored liquid,B.P. 104" l'10 C. at 0.08 mm. mole of the iodide (on the basis ofiodine-equivalency; Hg, 144-l46 C. at 3 mm. Hg, density at 20 C. foreach "mole of tetra-alkali metal pyrophosphate It 1 1848, refractiveindex nD O '1.-4222 In the presis believed that the iodine or iodidesalt catalyst first reence of water, tetraethyl pyrophosphate hydrolyzesrapacts with the ethyl chloride to form the highly reactive idly, andloses its insecticidal potency This is desirable ethyl iodide The ethyliodide than reacts with the tetrasince it will decompose after killingdestructive insects a ali metal pyrophosphate to "form the tetraethylpyrowithout the deposition of a lasting toxic residue on fruit,phosphate, and regenerate the iodide ion. The latter flowers or othercrops sprayed with the insecticide then reacts with a further proportionof ethyl chloride to e present invention is based on the discovery thatorm more ethyl iodidt'e Ethyl iodide itself is a very tetraethylpyrophosphate can be prepared by reaction of expensive reagent and itsuse in the commercial preparaethyl chloride with an alkali metalpyrophosphate as for tion of tetraethyl pyrophosphate is commerciallyimpracexample, tetrasodium pyrophosphate and tetrapotassium tical By theuse of the small amounts of the catalysts pyrophosphate with thereaction being in accordance of this invention it is feasible to avoidthe use of this with the following using tetrasodium pyrophosphate 'as40 expensive reagent and still to obtain satisfactory yields anillustration. of the tetraethyl pyrophosphate.

021350 003m The reaction of this invention may be effected attemperatures as low as about '40" C. owever, at this tem- 402E501N24Pg07 i 4NaCl /P -P\ perature, the reaction is somewhat slow. Themaximum CZHEO g g OOZHlS temperature at which this reaction may beeffected is In the absence of catalysts, and in the presence or absencelimited by the fact that above tetra'lethyl of solvents or suitablereaction media, the reaction propyrophosphate commences decompose Withllbefal ceeds slowly and with unsatisfactory yields. However, evolutionOf Y 11118, the 'feacll'on temperature ii the reaction is carried out inthe presence of an-iodide range effectively fllmlied t from about 40 C.to 165 as a catalyst, and for example, in the presence of a cata- 50 CSatisfactory y lds are Obtained Within the tem eralytic amount ofiodine, hydroiodic acid, ammonium iodide, lure T211136 511198 the ethylchloride and the iodides f the metals, alkahlleearth metals, most of thesolvents and reaction media suitable for this and the like, thisreaction may be elfected at a highly Process descrlkfe'd above boilbelow thls temperature praeheal rate Whh ehtamment f good ylelds f therange, it is desirable to efiect the reaction in autoclaves desiredproduce or in closed reaction vessels suitable for pressure, and

Because of the sensitivity of the end product tetraethyl With good 28 lStirling pyrophosphate in Water, the phosphate salts used in the Thereaction time, or Tesldence P d Wlthln the autoprocess of this inventionmust be anhydrous The ethyl clave of Pressure Vessel may Vary WldelyOver a great chloride may be employed in the reaction in theoreticalrange and Is by no means 9 being largely proportions, i e. at least fourmoles of ethyl chloride for Pendent on the SIZE 0f e at h o s a rule, atwo every mole of tetra-alkali metal pyrophosphate. How to three hourreacnon so Is i' ever, it is desirabla to employ a 100% to 200% molarable for the obtainment of satisfactory yields By this excess, 1 e.eight to twelve moles of ethyl chloride for E 29 5; g h gi g gi ihgi sigi t i siy each mole of tetra-alkah.metal pyropil'osphate' Smce cycle. Onthe basis of recovered ethyl chloride and the the excgss of ethylchloride can readily be recovered yields based on the ethyl chlorideactually consumed, after each cycle, and returned to the process, theuse of the yields are of the Order of 95% of theory In the Fthyl chlondeno Way represents an the absence of the iodide catalysts of thisinvention, mm dlsablhtythe yields per cycle are of the order of l5%-20%per The reaction may be effected in the absence of solvents. 70 cycleHowever, it has been found elfecting the reaction in the presence of acertain solthat best yields are obtained At the conclusion of thereaction, the reaction mixture is cooled and the mixture is thenfiltered. The insoluble material comprises the sodium chloride formed bythe reaction and excess (unreacted) tetrasodium pyrophosphate. Thefiltrate is then distilled to recover the excess of ethyl chloride,which may be returned to the process. The iodine or iodide used as acatalyst will be present in this filtrate in the form of ethyl iodide(which is formed by the reaction of the ethyl chloride with the iodineor iodide salt). This is recovered and recycled with the ethyl chloride,and may be used as the catalyst in the next step. Thus, ethyl iodideitself may be used as a catalyst in this process, whether added as suchin the first cycle of the process, or whether it is formed in the firstcycle by reaction of the iodide with ethyl chloride and recovered in thesubsequent cycles. The ethyl iodide boils at 72 C., and may be recoveredWith the solvent and reaction medium (i. e. the ketone or esteremployed), and recycled to the process for use in the subsequent runs.If any iodide is lost in each cycle, it may be made up by the periodicaddition of fresh catalyst, to bring the iodide equivalency up to fromabout 0.01 to 0.10 mole for each mole of anhydrous tetra-alkali metalpyrophosphate employed.

After filtering off the insoluble salts, distilling off (and recovering)the ethyl chloride, ethyl iodide and reaction medium (e. g., ketone orester), the oily residue of crude tetraethyl pyrophosphate remainingbehind may be employed as such, without further purification. Ifdesired, it may be further purified by distillation under reducedpressure. Tetraethyl pyrophosphate may be distilled withoutdecomposition at temperatures as high as 140-142 C., under a vacuum of 2mm. Hg.

Because of the insoluble nature of the tetra-alkali metal pyrophosphate,it is desirable that it be employed in as finely subdivided a state aspossible, i. e. ground to a fineness of at least 60-100 mesh. Aspreviously indicated, this reagent should be used in a substantially dryor anhydrous state to avoid premature hydrolysis of the tetraethylpyrophosphate.

The following embodiment is given to define and to illustrate thisinvention but in no 7 agents, proportions or conditions describedtherein.

Obvious improvements will occur to persons skilled in the art.

A mixture of 282 gms. of finely powdered anhydrous tetrasodiumpyrophosphate (1.0 mole), 7.5 gms. of sodium iodide catalyst (0.05mole), 646 gills. of ethyl chloride (10.0 moles) and 500 gms. of methylethyl ketone (as solvent and reaction medium) is charged into anautoclave, heated to 80-100 C. for two hours, with good agitation. Atthe conclusion of this period, the contents of the autoclave are cooled.Excess ethyl chloride is vented (and may be recovered and recycled). Thereaction mixture is filtered from insoluble sodium chloride andtetrasodium pyrophosphate and the filtrate is distilled to a pottemperature of 90 C. to provide a distillate containing the methyl ethylketone and the ethyl iodide formed during the reaction. This distillate4 may be returned to the process for use in the subsequent runs assolvent and catalyst (the ethyl iodide). The oily residue in the stillis then fractionated under reduced pressure. The tetraethylpyrophosphate distills over at l40-145 C. at 2-3 mm. Hg pressure, as aure compound.

While there is above disclosed but a limited number of embodiments ofthis invention herein presented, it is possible to produce still otherembodiments Without departing from the inventive concept hereindisclosed, and it is desired therefore that only such limitations beimposed on the appended claims as are stated therein.

What is claimed is:

1. A process for the manufacture of tetraethyl pyrophosphate whichcomprises reacting ethyl chloride with a member from the groupconsisting of tetrasodium pyrophosphate and tetrapotassium pyrophosphateat a temperature of about 40 C. to about 165 C. in the presence of acatalytic amount of an iodide.

2. A process, as defined in claim 1, wherein at least four moles ofethyl chloride are employed for every mole of tetra-alkali metalpyrophosphate.

3. A process, as defined in claim 1, wherein eight to twelve moles ofethyl chloride are employed for every mole of tetra-alkali metalpyrophosphate.

4. A process, as defined in claim 1, wherein the catalyst employedconsists essentially of from 0.01 to 0.10 mole-equivalent of iodine perevery 1.00 moleof tetra-alkali metal pyrophosphate employed. 1

5. A process, as defined in claim 1, in which the reaction is carriedout in the presence of methyl ethyl ketone.

6. A process, as defined in claim 1, carried out at a temperature ofabout C. to about f C.

7. A process, as defined in claim 1, wherein an inorganic iodide isemployed as a catalyst, is converted in the reaction to ethyl iodide,and is recovered as such. 8. A process, as defined in claim 1, whereinthe catalyst is sodium iodide.

9. A process, as defined in claim 1, wherein the catalyst is ethyliodide.

10. A process, as defined in claim 1, wherein the reaction is carriedout in presence of a lower aliphatic ketone. 11. A process, as definedin claim 1, wherein the reaction is carried out in presence of a loweraliphatic ester.

References Cited in the file of this patent Kosolapoff:Organo-Phosphorus Compounds," p. 337, John Wiley & Sons, New York, N. Y.(1950), citing: Cavalier: Compt. rend. 142, 885 (1906).

Clermont: Ann.9l, 375 (1854).

Hall et al.: Ind. Eng. Chem. 40, 694 (1948).

Rosenheim et al.: Ber. 41, 2708 (1908).

1. A PROCESS FOR THE MANUFACTURE OF TETRAETHYL PYROPHOSPHATE WHICHCOMPRISES REACTING ETHYL CHLORIDE WITH A MUMBER FROM THE GROUPCONSISTING OF TETRASODIUM PYROPHOSPHATE AND TETRAPOTASSIUMPYROSPHOSPHATE AT A TEMPERATURE OF ABOUT 40*C. TO ABOUT 165*C. IN THEPRESENCE OF A CATALYTIC AMOUNT OF AN IODIDE.